W3C home > Mailing lists > Public > public-html@w3.org > March 2011

RE: Change proposals for issue-152

From: Ian Hickson <ian@hixie.ch>
Date: Tue, 22 Mar 2011 19:46:42 +0000 (UTC)
To: Sean Hayes <Sean.Hayes@microsoft.com>
cc: Philip Jägenstedt <philipj@opera.com>, "public-html@w3.org" <public-html@w3.org>
Message-ID: <Pine.LNX.4.64.1103221937040.25791@ps20323.dreamhostps.com>
On Tue, 22 Mar 2011, Sean Hayes wrote:
>
> Well I don't agree that the "whole point of having multiple text tracks 
> is that the user agent can intelligently avoid overlapping cues while 
> ensuring that a single cue doesn't move around when other cues are added 
> or removed at the same time" is true, in fact I'm not sure I even 
> understand what you mean by that; why is there a need to fix a caption 
> once placed?

You don't agree with it but you don't know what it means? :-)

I mean a case where caption A (a long caption) is from time 0s to 4s, 
caption B is from 3s to 5s, and caption C is from 4s to 8s.

At times 1s, 3.5s, 4.5s, and 6s, in the absence of any explicit 
positioning, the IMHO ideal renderings would be:

 1s
 +--------------+
 |              |
 |              |
 | AAA AAAA AAA |
 |  AAA AAA AA  |
 +--------------+

 3.5s
 +--------------+
 |              |
 |    BBBBBB    |
 | AAA AAAA AAA |
 |  AAA AAA AA  |
 +--------------+

 4.5s
 +--------------+
 |              |
 |    BBBBBB    |
 |              |
 |              |
 +--------------+

 6s
 +--------------+
 |              |
 |    BBBBBB    |
 |              |
 |     CCCC     |
 +--------------+


> If you are saying that captions are going to be selected in and fixed in 
> space in temporal order; that makes no sense, as you will end up with 
> different streams interleaved. it's actually far more likely you would 
> want to assign each caption output a fixed distinct region, since the 
> 80% use case for multiple simultaneous cue tracks is mixed language 
> subtitling like Bollywood where they subtitle in both Urdu and Hindi, 
> one individual reader is only going to be looking at one of the streams 
> so they want to always flick eye-gaze directly to where those captions 
> are going to appear.

Certainly by default streams should appear in the same place as other 
cues from the same stream. However, we never want cues to jump around. 
This is a stateful temporal issue which is out of scope for CSS. We should 
use CSS for styling, but not for things it isn't suited for. (Another 
example of what we shouldn't use CSS for is semantics.)

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Tuesday, 22 March 2011 19:47:13 UTC

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